Doc: Test task documentation incomplete

Hello.

I noticed the following issues in the Test task documentation:

  • It starts with Executes JUnit (3.8.x or 4.x) or TestNG tests., although JUnit 5 is now supported.
  • The example and various other parts of the page mention the method Test.useJUnitPlatform(), but this method isn’t listed in the list of methods, with useJUnit() and useTestNG()